6.9 trouble starting warm - PeachParts Mercedes-Benz Forum

gs sparhawk · #1 02-06-2009, 12:51 AM

1979 6.9 starts fine cold and then when warmed and stopped, it seems as if there is no fuel getting to it since I have to put the throttle down and then it coughs, sputters & runs fine.

I've tried a few sites & searches but no luck. One of those warm up/cough up valves or some quirky 6.9-specific troubles, I suppose.

sparky

alabbasi · #2 02-06-2009, 01:04 AM

leaky injectors, a leaky cold start injector or a problem with accumulator could cause this.
There are some pretty good BOSCH CIS books out there which will describe these issues and how to diagnose them.

gs sparhawk · #3 02-06-2009, 02:13 AM

Thanks, Al. Seems that a few other threads mention the accumulator and the tests. I'll give that a go (when I can dedicate the time) and see if that does it. This one has a few vac lines disconnected here and there by some PO or a goat that may have stumbled through at some time. Lots of very brittle plastic lines that may be broken almost anywhere. I keep finding them while doing other stuff. It's a wonder it goes at all. I have a local "good guy" MB specialist that I may sick on it for the usual suspects and a prognosis. (Hoping, of course, that he doesn't find anything too daunting.)

I'm still very much on the shy side of value so I have some head-room yet and may still come out with a fine piece without breaking the bank.

Thanks for the continuing assistance.

Sparky

berfinroy · #4 02-08-2009, 09:36 AM

The 6.9 is prone to hot start problems due to the fact that modern alcohol laced fuels evaporate more readily. I read somewhere years ago when I had a 6.9 with the same problem that the fix is to have a clever mechanic wire the cold start valve to come on momentarily with the starter switch even when the motor is hot. I never bothered to do it on my car.